1. Field of the Invention
The present invention relates generally to an organic source boat structure for organic electro-luminescent display fabricating apparatus and, more particularly, to an organic source boat structure for organic electro-luminescent display fabricating apparatus having a structure for uniform deposition of organic source.
2. Description of the Related Art
As a self luminescent display having a wide view angle, an organic electro-luminescent display has been fabricated in a small and medium size to a large size and it is generally known as a next generation display capable of applying to wide areas including military use, office use and PDA.
The organic ELD has a multi-layered organic source layer structure between an anode ITO electrode layer and a cathode metal electrode layer formed on a glass substrate, wherein the organic source layer structure comprises a hole injection layer for injection of holes, an electron injection layer for injection of electrons and an organic luminescent layer interposed between the hole injection layer and the electron injection layer, emitting light by combination of the hole and the electron.
Generally, a device for fabrication of the organic EL device employs an organic source boat for evaporation of the organic source. The organic source boat is fabricated in a shape of crucible with ceramic or other materials having a low heat conductivity and a large heat capacity for prevention of sudden temperature rise and for stable heating.
FIGS. 1A and 1B show an organic source boat applied when one organic layer is formed by one organic source. Referring to FIG. 1A, a heating coil 12 is rolled around an organic source boat 10 in order to evaporate organic source. Referring to FIG. 1B, an organic source boat 14 is in a shape of plane plate and organic source is provided on a heating panel 16.
Therefore, the organic source boats 10,14 of FIGS. 1A and 1B are desirably applied in forming a single-layered organic source layer without doping when a small-sized panel is fabricated. In this case, it is possible to form an organic layer by one organic source boat 10, 14 while maintaining uniformity.
However, according to organic source boats 10,14 of FIGS. 1A and 1B, it is difficult to maintain uniformity of organic layer formation when they are applied to a large-sized panel, due to distance difference from organic source.
And, when an organic source layer is formed by a doping method using 2 or more organic sources, a simultaneous deposition method is employed. According to the method, a plurality of organic source boats are simultaneously heated, thereby simultaneously forming organic layers, as shown in FIG. 1C.
Referring to FIG. 1C, a first organic source boat 20a for evaporation of host organic source and a second organic source boat 20b for evaporation of dopant organic source are provided, thereby simultaneously depositing host organic source and dopant organic source.
Here, when the host organic source and the dopant organic source are simultaneously deposited by the organic source structure of FIG. 1C, a distance difference of organic source boats 20a and 20b is generated to the center of substrate and the outside, thereby lowering uniformity of mixing ratio between host organic source and dopant organic source deposited on the substrate.
That is, host organic source and dopant organic source are thickly formed in the long distance from corresponding organic source boats 20a and 20b and thinly formed in the short distance. Therefore, a difference is generated in doping concentration of dopant according to the position on the substrate, thereby respectively generating a low concentration region and a high concentration region.
Here, a dopant of organic EL device performs an essential part of luminescence, wherein chroma and efficiency of luminescence are determined by concentration of dopant and thickness of organic source layer. Therefore, brightness and chroma of luminescence and electrical properties of device are deteriorated by a concentration difference in luminescence layer of doped organic molecules. As a result, it is difficult to successfully form thickness and dopant distribution of organic source layer as a determinant of device properties in organic EL device having multi-layered organic source layer with organic source deposition structures shown in FIGS. 1A to 1C.
FIG. 2 shows an organic source boat structure having improved loading capacity of organic source and doping efficiency of dopant according to another conventional method.
The organic source boat 30 has a united structure comprising a first evaporation unit 32 for deposition of host organic source and a second evaporation unit 34 for deposition of dopant organic source, wherein the first evaporation unit 32 is disposed on the circularly-separated external side, having the same axis with the second evaporation unit 34 and the second evaporation unit 34 is disposed on the internal side thereof (that is, on the center of corresponding organic source boat 30).
According to FIG. 2, the organic source boat 30 has a separated structure of the first evaporation unit 32 for evaporation of host organic source and the second evaporation unit 34 for evaporation of dopant organic source. Therefore, it is possible to separately heat the host organic source and the dopant organic source and to separately control the deposition rate. And, it is also possible to evaporate in a radial shape around the center of substrate 36.
As a result, according to the organic source boat of FIG. 2, the first and the second deposition units 32,34 are separately formed for deposition of host and dopant organic sources, thereby having improved uniformity of organic source layer, compared with structures in FIGS. 1A to 1C. However, the organic source boat has a circular evaporation structure having the same axis, thereby respectively generating a thick region and a thin region of organic source deposited on the substrate 36. That is, as evaporation processes, evaporated organic source layer becomes thicker in xe2x80x98Axe2x80x99 part close to the center of organic source boat 30 than xe2x80x98Bxe2x80x99 part at a long distance thereof, thereby affecting doping concentration of dopant organic source.
Therefore, the present invention has been made to solve the above problems and an object of the present invention is to provide an organic source boat structure for organic electro-luminescent display fabricating apparatus having improved loading capacity of host/dopant organic source and maintaining uniformity of organic source layer with a point symmetrical structure.
In order to accomplish the above object, the present invention comprises: a plurality of host cells having a plurality of evaporation holes for evaporation of host organic source; a plurality of dopant cells alternatively arranged to the plurality of host cells, having a plurality of evaporation holes for evaporation of dopant organic source; contamination control plates arranged between the host cells and the dopant cells; and a side cover to stably support the host cells and the dopant cells.
According to the present invention, the host cell and the dopant cell are formed in a pie shape wherein the area is increased from the center to the outside and a cylindrical shape is formed by the side cover.
And, the host cell is formed larger than the dopant cell.
It is desirable that evaporation holes of the host cell and the dopant cell are formed with regular distances to the diameter direction and to the arc direction.
And, a cooling water circulatory structure is formed in the contamination control plate.
According to the present invention, the host cell and the dopant cell comprises a cell body for deposition of the host/dopant organic sources, a heater coil rolled around the cell body and a cap having the evaporation hole.
According to the present invention, the host organic source and the dopant organic source are evaporated through evaporation holes formed with regular distances to the diameter direction and to the arc direction from alternatively-arranged a plurality of host cells and dopant cells and then, deposited on the substrate. And, contamination control plates are arranged between the host cells and the dopant cells, thereby preventing bad influence by evaporation of adjacent cells. And, cooling water is circulated in the contamination control plate in order to prevent temperature rise of the plate and therefore, to form uniform organic source layer.